Beetle menage

When I spotted two large beetles scurrying close together on the ground, my first thought was "it's a fine morning for mating." But as I watched the guy doing what looked like tearing off his potential mate's elytra—her wing covers—my next thought was that this was pretty extreme bodice-ripping. In fact, it looked a lot like predation. And what was that little beetle doing? Watching? Getting ready for a snack? Trying to get in on the sexual action while the big guy wasn't paying attention? Perplexed, I did what any naturalist would do: I sent the photo off to Arthur V. Evans, the author of the brand new Beetles of North America, a marvelous guide to these insects from the Princeton University Press. Dr. Evans graciously told me that the beetles are in the genus Prionus and the guy was not practicing overly rough love. The female's elytron was simply malformed. She was not about to be prey. I'm still waiting for an answer on what the little guy was doing.